In the matter of stirring liquids by apparatus in lieu of hand stirring, the attempt has always been to obtain circulation of the liquid composition within the container. The greater degree of circulation results in improved intermingling and homogenizing of the composition for better dispersion of particles within the liquid. In many instances, heat must be applied to the container in addition to the stirring action to achieve the desired results. In other instances, such as certain laboratory work, heating must be avoided, be it from external sources or as can be developed by the varied motion and operation of the stirring apparatus.
The path to be followed by the stirrer can enhance the stirring if the proper motion is imparted to the stirrer. In contrast, stirring will be ineffective if the path of the stirrer does not cause the necessary motion within the liquid composition. It is most desirable if the stirrer can impart motion to the liquid so that the liquid moves in a vertical direction and at the same time in a horizontal direction.
Some of the prior art oscillating stirrers were of a type which could be referred as plungers, that is the stirrer is moved up and down in a generally vertical plane. The stirrer frequently has some device attached at or near the end portion in the liquid to impart motion to the liquid. In some instances the stirrer actuator will impart heat to the liquid which may be undesirable particularly in laboratory work. To reduce or eliminate the heat problem, use began to be made of stirrers driven by application of alternating, positive and negative pressures to the interior of a reactor vessel containing vertically moving rod having an enlargement on the lower end. U. S. Pat. No. 3,484,204 is such type stirrer. My co-pending U. S. Pat. application No. 458,846 is a marked improvement over the prior art in that a pair of novel abutment plates are secured to the inner surface of a diaphragm supporting the stirring rod and stroke a metal disk into the diaphragm. The abutment plates are of unequal length and height in accordance with the principles of their design as disclosed in this application. Use is made of single phase ACA to impart motion to the diaphragm and the result is that the stirring motion is in an inclined elliptical path lined in X, Y and Z planes. The stirring apparatus of this application can be secured to the various types of closures for flasks or other containers, such as the Corning Glass "Fleaker" flask or the familiar Kontes flask but the flasks should be kept vertical.
The application of the apparatus in my co-pending U. S. Pat. application No. 458,846 with the "Fleaker" flask and a Kontes flask has been quite successful. However, it has been found that occasionally under certain working conditions there was a build-up of pressure particularly in the Fleaker flask which could impair or even halt the flexing of the diaphragm. Also it was found that application of the apparatus disclosed in that application was difficult with closures of varying types also used with laboratory flasks.